* contrib/lisp/org-e-texinfo.el: Added support for optional menu titles, also do not create menu entries for non-exporting headlines

(org-e-texinfo--generate-menu-items): Use optional title in menu if
present.
(org-e-texinfo-headline): Use optional title in node entry if present.
(org-e-texinfo--generate-menu-list): Omit headlines with :noexport:
tag when generating menu entries.